The present document is based on Japanese Priority Document JP 2001-204406, filed in the Japanese Patent Office on Jul. 5, 2001, the entire contents of which being incorporated herein by reference.
1. Field of the Invention
The present invention relates to a light emitting and receiving device structure suitably employed in an optical apparatus for bar code reading, and more particularly to improvement techniques which enable miniaturization and lightweight of such device structure to be achieved by adjusting arrangement of a light emitting element and a light receiving element.
2. Description of the Related Art
Recently, a great many stores, shops, factories and the like put bar codes on their goods and products for sales control and production management. The bar codes, each representing digital information, are read by optical scanning. In general, by irradiating beams of light to the bar codes and subjecting the intensity of reflected beams of light to photoelectric conversion, this type of bar code provides information from a combination of detected signals therefrom.
Namely, as shown by a conceptual representation in FIG. 5, a beam of light from a light emitting element 1 is focused through an iris of a light projection lens 3, and the beam of light thus obtained is reflected off a mirror 7 of a scan mirror 5 to irradiate a bar code pattern 9 which is a target of irradiation. Since the beam of light is irradiated over the entire area of the bar code pattern 9, the mirror 7 is oscillated. The oscillation occurs as follows: by fitting a magnet 11, which is attached to the mirror 7, into a drive coil 13, for example, positive and negative current is applied to the drive coil 13 at a constant period, then the magnet 11 is attracted to and repelled from the drive coil 13, thus causing the mirror 7 to oscillate relative to an oscillating fulcrum point 15 as its fulcrum.
On the other hand, the beam of light irradiated on the surface of the bar code pattern 9, despite undergoing irregular reflection, returns to the mirror 7 again through changes in the quantity of light due to the black and white of the bar code pattern. Then, the beam of light reflected there is condensed by a condenser lens 17, changes in the quantity of light being electrically converted by a light receiving element 19 and outputted. It should be noted that for the sake of increasing the reading accuracy, a band pass filter (BPF) is set up in front of the light receiving element 19 to prevent admitting unnecessary beams of light other than those beams of the light emitting optical frequency.
A light emitting and receiving device for bar code reading shown in FIG. 6 is available as a conventional apparatus which is constructed in accordance with the above-mentioned bar code reading method. The light emitting and receiving device is, as illustrated, configured by a light emitting assembly A incorporating a light emitting element 1 and a light projection lens 3 in a housing 25 and a light receiving assembly B incorporating a light receiving element 19 and a light receiving lens 17, and a BPF 21 in a housing 27. Both assemblies are mounted on a substrate 29.
Electrical connections in each of the housing 25 and the housing 27 are performed by wire bonding or other methods, and the mirror 7 of the scan mirror 5 is so arranged as to enable oscillation relative to the oscillation fulcrum point 15. Further, these light emitting assembly A, light receiving assembly B, and scan mirror 5 are accommodated in a frame not illustrated to form a light emitting and receiving device for bar code reading.
Nevertheless, since the light emitting and receiving device for bar code reading comprises the light emitting assembly with the light emitting element and the light projection lens accommodated in a casing separately from the light receiving assembly B with the light receiving element and the light receiving lens accommodated in another casing, there are a large number of parts. In addition, because the light emitting element and the light receiving element need to be juxtaposed facing a target of irradiation, a gap occurs between the packages to necessitate a large installation space, setting limits to achieving miniaturization and light weight of the entire light emitting and receiving device.
On the other hand, miniaturization may be conceivably accomplished by juxtaposing and incorporating the light emitting element and the light receiving element in a single package, while, on the other hand, an area due to package duplication can be dispensed with by constructing an integral, one-piece package, but the need to secure the spaces for mounting the light emitting element and the light receiving element on the same plane yet remains, thus making it impossible to accomplish sufficient miniaturization.
Further, in a case of juxtaposing the light emitting element and the light receiving element on the same plane, the optical axis of an emitted beam of light cannot be placed in close proximity to the optical axis of a return beam of light, so that the light projection lens is disposed on the outside face of the light receiving lens, contributing to enlarging a space occupied by the optical systemxe2x80x94another detriment to achieving miniaturization and light weight of the light emitting and receiving device.
The present invention is directed to solving these drawbacks, and provides a light emitting and receiving device structure which can place an optical axis of an emitted beam of light in close proximity to an optical axis of a return beam of light, thereby accomplishing the miniaturization and light weight of the light emitting and receiving device.
A light emitting and receiving device structure according to a first aspect of the present invention comprises a cylindrical package having a bottom with an opening on one end and the other end closed, and a pedestal member concentric with a center line of the package and protrudingly disposed on a bottom plate in the package. In the device structure, the light receiving element is secured to a front end surface of the pedestal member and the light emitting element is secured to a side face of the pedestal member, so that the light emitting element and the light receiving element are both accommodated in the same package.
In the light emitting and receiving device structure, each surface (the front end surface and the side face) of the cubic pedestal member protrudingly disposed on the bottom plate of the package is utilized for a space of mounting each element; for example, as compared with a structure of juxtaposing a light emitting element and a light receiving element on the bottom plate, the present arrangement can provide high-density accommodation by making an outer diameter of the package small. Namely, the miniaturization of the package becomes possible.
Further, through this structure of element arrangement in this manner, it is possible to place an optical axis of an emitted beam of light in close proximity to an optical axis of a return beam of light, enabling a light projection lens to be easily placed on a region of the light receiving lens, whereby a medium is jointly used (made possible by a one-piece light projection and receiving lens with the formation of a light projection lens element on a part of the light receiving lens) to enable an optical system to be made lightweight.
A light emitting and receiving device structure according to a second aspect of the present invention comprises a strip of light emitting element of having a light emitting unit on an end surface and irradiating a beam of light emitted from the light emitting unit to a target of irradiation; a strip of light receiving element of having a light receiving face on a surface thereof and receiving a return beam of light from the target of irradiation on the light receiving face; a cylindrical package having a bottom with an opening on one end and the other end closed by a bottom plate; and a pedestal member protrudingly disposed on the bottom plate in the package in such a manner as to be concentric with the center line of the package. In the device structure, the light receiving element is secured to the front end surface of the pedestal member so that the light receiving face looks towards the opening and the light emitting element is secured to the side face of the pedestal member so that the light emitting unit looks towards the opening.
In the light emitting and receiving device structure having been described, in addition to its space-saving feature, the orthogonal surfaces (the front end surface and the side face) of the cubic pedestal member protrudingly disposed on the bottom plate of the package are put to effective use as the spaces of mounting the elements to enable respective strips of light emitting element and light receiving element to be placed at right angles relative to each other, whereby, for example, as compared with a conventional structure of juxtaposing the light emitting element and the light receiving element on one bottom plate, an outer diameter of a package can be made small to provide for high-density accommodation, that is, enabling the package to be made compact.
Further, the configuration of the devices in this way makes it possible to place an optical axis of an emitted beam of light in close proximity to an optical axis of a return beam of light, hence, the light projection lens can be arranged on the region of the receiving light lens, whereby a medium can be jointly used to enable the optical system to be made light weight.
The light emitting and receiving device structure according to a third aspect of the present invention comprises an one-piece light projection and receiving lens having a light projection lens unit formed on a part of the light receiving lens unit, which is secured to the opening of the package.
In the light emitting and receiving device structure, the light receiving lens unit of the one-piece light projection and receiving lens is fitted into the entire opening of the package, the light projection lens unit being formed on a part of the light receiving lens unit, thereby making it possible to converge the emitted beam of light and the return beam of light even in the high-density device configuration. In the device structure, an optical axis of the emitted beam of light is placed in close proximity to an optical axis of the return beam of light. Further, the light projection lens can be set up in a space for setting up the light receiving lens, and the space for setting up the optical system becomes smaller by dispensing with a space which would otherwise be required therefor. In addition, the weight becomes lighter.
The light emitting and receiving device structure according to a fourth aspect of the present invention includes the pedestal member composed of a heat sink.
In the light emitting and receiving device structure, since the pedestal member is composed of the heat sink, the pedestal member has a dual function as a pedestal for cubic arrangement of the light emitting element and the light receiving element and as means for cooling the devices, thus realizing an advanced function (additional cooling function) while maintaining its miniature size.
The light emitting and receiving device structure according to a fifth aspect of the present invention comprises a plurality of leads that extend through the bottom plate and protrude in a ring space between an outer circumference of the pedestal member and an inner circumference of the package, respective leads being connected to electrodes of the light emitting element and the light receiving element.
In the light emitting and receiving device structure, by placing the pedestal member protrudingly on the bottom plate, the ring space is formed between the inner circumference of the package and the outer circumference of the pedestal member. By letting the plurality of leads that extend through the bottom plate protrude into the ring space, the leads can be placed at any position in the circular direction, thus making effective use of the ring space possible. This allows electrical connections while maintaining the miniaturization of the package without providing for a space exclusively for lead connections.
In accordance with the light emitting and receiving device structure of the present invention, the pedestal member is protrudingly disposed on the bottom plate of the cylindrical package having a bottom, the light receiving element being secured to the front end surface of the pedestal member and the light emitting element being secured to the side face of the pedestal member, hence, as compared with a case of using each surface (the front end surface and the side face) of the cubic pedestal member for a space of mounting each device, for example, juxtaposing the light emitting element and the light receiving element on the bottom plate of the package, the outer diameter of the package is made small to enable high-density accommodation. Namely, it is possible to make a compact structure, hence the package can be made smaller. Use of the structure for disposing the devices in this manner makes it possible to place the optical axis of the emitted beam of light in close proximity to the optical axis of the return beam of light, and the light projection lens can be disposed on the region of the light receiving lens, whereby it is possible to produce an one-piece light emitting and light receiving structure jointly using a medium, resulting in the lightweight light emitting and receiving device.